The Das-1 immunostain is useful for discriminating metastatic colon adenocarcinoma from cholangiocarcinoma and hepatocellular carcinoma.

The distinction between cholangiocarcinoma, hepatocellular carcinoma and liver metastasis is important but at times difficult solely on microscopic appearances. The Das-1 immunostain exhibits specificity for colonic epithelium. However, its staining of cholangiocarcinomas and hepatocellular carcinomas has not been extensively studied. We evaluated the staining properties of the Das-1 immunostain in cholangiocarcinoma and hepatocellular carcinoma. Forty-four cholangiocarcinomas, 16 hepatocellular carcinomas, 17 colon adenocarcinomas metastatic to the liver and 3 benign biliary tumors were studied. The cases were stained with the Das-1 antibody following deparaffinization and rehydration. The slides were evaluated for membranous and/or cytoplasmic staining in a blinded fashion. The percentage of tumor cells exhibiting strong staining was estimated. Of the intra-hepatic cholangiocarcinomas, 4 of 36 (11%) and 2 of 16 (13%) hepatocellular carcinomas were positive for Das-1, though typically only in rare cells. In comparison, 7 of 8 (88%) extra-hepatic cholangiocarcinomas, 13 of 17 (77%) of metastatic colon carcinomas and 3 of 3 (100%) benign tumors of the biliary tract were strongly positive in a diffuse pattern. The Das-1 immunostain may play a useful role in evaluating liver malignancies.